Gas Well De-Liquification WorkshopDenver, Colorado
February 28 - March 2, 2005
Artificial Lift Selection for Gas Well Deliquification
J Lea, Texas TechRobert Lestz, Chevron/Texaco,Cleon Dunham, ALRDCO. Fasokun, Texas Tech
Selection of Deliquification Method
• There is no generally accepted method
• There are many factors to consider
• This could be subject of best practice… API or otherwise
• Consideration of some factors can lead to improved selection
• Some (not all) important factors considered here
Some Popular Methods1. Electrical submersible pumping2. Progressing cavity pumping3. Beam pumping4. Hydraulic pumping5. Gas lift 6. Velocity strings7. Compression systems8. Plungers9. Foaming10. Injection systems
Artificial Lift Selection Process
1. Make a Rough Cut with Artificial Lift Screening Criteria
2. Review Feasibility / Functionality of Artificial Lift Methods
3. Evaluate Cost --- CAPEX, OPEX
4. Consider Availability, Use of Reservoir Energy
5. Consider Availability of Required Infrastructure
6. Consider Availability of Required Operator Training
Artificial Lift SelectionMethod CAPEX Elec Line Reser Oper
1. ESP 115,000 Y L2. PCP 35,000 Y M3. Beam 45,000 Y M4. Hydraulic 45,000 Y M5. Gas lift 25,000+ Y M6. Velocity String 10,000 Y L7. Compression 20,000 Y M8. Plungers 7,500 Y M-H9. Foaming 10,000 Y H10. Injection 40,000 Y L
Figure 1: Critical gas rate required vs. Wellhead Pressure (Coleman et al., see Reference 1)
Increase Rate above Critical with Gaslift, Velocity String, Compression or Foam
Estimate Operating Power Cost from Efficiency Definition
• Operating Costs: – Power efficiency may be defined as: as a fraction
of the power used to lift liquids divided by the total power supplied.
– Assume 20hp load for all methods (when applicable), 4000’ lift, 20 bpd, sp gr =1.0 and efficiency as defined below. Assume 200 bpd for high rate lift methods.
– kW = .00000736 x 20 x 4000 x 1.0 x 0.746/ η = 0.4356/η
• Assume electrical costs of $0.08/ (kW-hr)– $/year = 0.4356 x 0.08 x 365 x 24 / η = 305 / η– $/year ≈ 300/η for low rate case of 20 bpd– $/year ≈ 3000/η for high rate case of 200 bpd
Method: ηESP 40PCP 60Beam 50Hydraulic jet 20Gas lift 20Velocity strings -Compression 80Plungers -Foaming -Injection systems -
Screening of Artificial Lift Methods
Artificial Lift Screening for Deliquification of Gas WellsLegend:++ Very well suited for this situation+ Well suited for this situation+/- May be OK, depending on details- Poorly suited for this situation-- Very poorly suited for this situationTable 1: Screening matrix for lift methods designed to lift liquids off gas wells.
++/-+/-+/--+/------Dual completion
+++++/-+/--+/-+/--Small casing
++++++++/-+/-+/-+/-Deviated
++++++++++++Shallow
+/-++++++/-+/-+/-+/-+Deep
Well Conditions
InjectVel StringFoamCompressPlungerGas-LiftHydraulicBeamPCPESPCharacteristic
Characteristic ESP PCP Beam Hydraulic Gas-Lift Plunger Compress Foam Vel String
Inject
+/-++-++/-----Corrosive
------------+/--Viscous
+/-++-++/-+/-+/-+/-+/-Sour
--++---+/---+/--Sandy
+-------++++Low GOR
++++++++++---+/--High GOR
++/-+++-+/-+++/-+/-Low BHP
-+++++/-+/-++++++High BHP
++/-+++++++/-+/-++/--Low production
+++-+/---+/-+/--+/-++High production
Production Characteristics
++++/-+/-----+/-Poor access to spare parts
++++++++++Ready access to spare parts
Access to Spare Parts
+/-++++/-++--+/-----No access to electrical power
+/-++++/-++-+/---Poor power
+/-++++/-++/-++++Good power
Access to Power
+/-++++/-+++/--+/-+/-+/-Remote
++++++-+++/---+/-+/-Developed
--+---+/----+/-Sub-sea
--+++/-+/-+++--+/-+/-Offshore
+++++++++++Onshore
Location
Characteristic ESP PCP Beam Hydraulic Gas-Lift Plunger Compress Foam Vel String
Inject
+/-+/-+/--+/-+/--+/---Limited operating
budget
++++++++++Adequate operating
budget
+/-+/-+/---+/--+/---Limited capital budget
++++++++++Adequate capital budget
Budget Support
+++/---+/--+/---Poor access to service staff
++++++++++Good access to service staff
++/-+/---+/--+/---Untrained operators
++++++++++Trained operators
+/-+/-+/-+/-+/-+/--+/---No engineers
++++++++++Trained engineers
Staff
Characteristic ESP PCP Beam Hydraulic Gas-Lift Plunger Compress Foam Vel String
Inject
Selection from Depth-Rate Charts
High Rate Lift Rate vs: Depth
After Weatherford
Low Rate Lift Rate vs: Depth
After Weatherford
Inflow / Outflow for Various Lift Methods
ESP, PCP, Beam, Hyd Recip, Injection
Gas Lift for Low Liquids
Gas Lift forHigh-Liquids, Velocity String, Compression, Foam, Jet
Plungers
Rate
Dra
wdo
wn
Selection from Decision Tree
Examples Presented
Monthly Production Data
Generate Velocity Profiles
no Does Available Data Indicate Liquid Loading
yes
Run Pressure Gradient Survey no Has a Pressure Gradient survey Been Run?
yes
Open All Cotton Valley Pay no Is All Cotton Valley Pay Open?
yes
Install Soap Injection yes Is Soap Injection Feasible?
no
Install Small Diameter Tubing yes Well Workover Scheduled?
no
Lower the Flowing Tubing Pressure yes Can the Flowing Tubing Pressure be Lowered?
no
Implement a Pseudo-Gas Lift System yes Can a Pseudo-Gas Lift System be
Implemented Without Killing the Well
no
Install a Plunger Lift yes Is Plunger Lift Feasible?
no
Install Gas Lift yes Is Gas Lift practical?
no
Install Beam Lift yes Is Beam Lift Practical?
no
Produce to Depletion
Plug & Abandon
Figure 4: An older selection chart developed for AL selection for gas
wells in East Texas
Selection Chart: For discussion
Check for loading:
•Critical velocity or rate?
•Falls off decline curve and stays there?
•Initiation of slugging?
•Difference between tbg-csg pressure increases with time?
•Other?
Team meeting:
•Establish stable rate (swab?)
•Determine gas rate, condensate rate, water rate
•Some operators check flowing pressure survey
Screen AL method considering conditions
Sand?
PCP, Gaslift,
Velocity String, Foam , some pumping methods
Hi-Rate?
ESP,
Gaslift,
Velocity String,
Beam,
Other?
Hi Surf P?
Compress,
Pump,
Other?
Lo Rate?
1. Swab,
2. Stop Clock,
3. Plunger,
4. Gaslift,
5. Foam,
6. Pumping methods
7. Other?
Preferred? For discussion:
1. Plunger (conventional, two piece, free cycle, other? if feasible)
2. Foam (soap sticks(shallow), batch treat with no packer, Cap tube injection with packer present if water and no high condensate.
3. Gaslift
4. Pumping methods (Beam, ESP, Diaphragm, PCP, Hydraulic, other?)
5. Consider special devices: Collar inserts, Vortex, Goal, other?
6. Inject water if feasible
Evaluation of Feasibilityof Different Artificial Lift
Methods
ESP’s• ESP’s operate from shallow depths to as deep as 10,000’ and
deeper. • They can produce low rates but below about 400 bpd, the
efficiency of the system suffers. • They can produce 20,000 bpd in some cases. • High temperatures can be a problem with a typical maximum of
275 oF up to 400 oF with special trim. • They are installed in deviated wells, but the unit must be landed
such that it is straight even if the wellbore is deviated. • Power must be available and is transmitted down a three phase
cable to the motor. • Small disposable units are used for shallow wells such as for
coal bed methane to lift water off the coal seams.• High solids concentrations may cause the unit to fail if they are
allowed to be pumped, although special abraision resistant units can be used.
PCP’s• PCP’s typically operate to 4500’ and in some cases to as deep
as 6000’.
• At shallow depths they can produce up to 4,500 bpd.
• With elastomeric stators, the maximum temperature is about 150 oF.
• They can be used up to about 250 oF with special elastomeric materials.
• With rotating rods they can be installed in wells with a deviation of 15°/100’, but if run with ESP motors, deviation is no problem as long as the unit is straight although the wellbore isdeviated.
• They can tolerate some sand production, and have high (40-70%) power efficiency.
• New materials may extend temperature limits.
Beam Lift• These systems have operated to 16,000’ but a depth of 10,000 -
11,000’ is more typical of maximum operating depths with more standard equipment.
• Can pump to up to 5,000 bpd at shallow depths but the maximum production rate is greatly reduced at greater depth.
• Less than 1,000 bpd is more typical for most mid-depth applications.
• They can be used in deviated wells with slow build angles.
• Efficiency is good (45-60%).
• For gas wells with small liquid rates, slender rods, small diameter pumps, and low horsepower may be sufficient.
Hydraulics• Both jet and reciprocating pumps can be run to 15,000’ or
below.
• Both can produce up to 10,000 bpd, depending on depths.
• Both can run in 250 oF wells.
• The reciprocating pump cannot tolerate solids.
• Clean pressured power water or oil must be supplied to the pumps to make them operate.
• For gas well de-watering applications, typically a jet pump producing a few hundred or much less barrels per day is more common. The power efficiency is poor and intake pressure is not that low.
Gaslift• Gaslift can be used to 10,000 ft or more.• Rates of 10,000 bpd or higher can be achieved. • Solids can be produced. • Valves are tubing retrievable.• High pressure gas is needed. • For slim holes, valves can be installed on slender tubing or coiled
tubing. • Wellbore temperatures to 250 oF are typical and can reach up to 400 oF
with precautions. • For gas well operation, typical rates are a few 100 bpd or less.
• For gas wells, you can recirculate gas at bottom of tubing with single point injection in some cases.
• With enough gas injected and with velocity over critical, the well will never liquid load
Velocity String• A velocity string can be used to 10,000’ or deeper.
• ID’s down to 1” are used although smaller ID tubing is hard to unload.
• Nodal analysis and critical velocity are used (see below) to help size the installations.
• Many successes are reported, usually for wells making more than several hundred bpd.
• For lower rates, plunger lift might be more applicable.
• String may have to be downsized even more in the future, where plunger could take the well do depletion
Compression• Compression is used for single wells or for multiple
wells. • Nodal analysis will help predict the expected results
to be achieved. • Lower well head pressure has many beneficial
effects. • Lower pressure keeps water in vapor state so this is
artificial lift method in itself• Biggest percentage gains for low pressure wells• Lower wellhead pressure improves artificial lift
methods in general as well as flowing wells
Plunger Lift• If a gas-liquid ratio of 300 - 400 scf/bbl/1000’ is present and
some buildup pressure is available, the well requires no outside energy to produce when using a plunger.
• Another industry guideline is the well pressure must be 1½ times the line pressure.
• Use Operating Pressure/GLR charts vs Depth>>>
• Plungers can produce from great depths.
• Typically a plunger installation requires that the packer be removed, although free cycle or two piece plungers may operate with the packer in place.
• Plungers usually produce a low liquid production rate, but in some cases can produce up to 300 bpd.
• Usually no outside energy is needed to operate the system.
Foam• Often foam is used as a first attempt to unload because
it is inexpensive to try. • It works much better with water and no condensate but
some expensive chemical agents are predicted to foam condensates.
• Use soap sticks in shallower wells and use batch treating or capillary tube injection for deeper wells depending on whether or not a packer is present.
• Usually if condensate is produced, foam is not used. • Chlorides indicate formation water and lack of chlorides
indicate condensation of water in the wellbore.• Typically foaming water reduces the required critical
velocity to 1/3 of value without surfactants.
Inject (water)• Use these systems when only water is produced (no
condensate) and if there is an underlying injection zone that will take the produced water.
• Back pressure on the tubing may help inject the water so gas can flow up the annulus.
• Frequency of use in industry is low.
• Western Kansas is area of reported use.
Economics
Initial Cost
Table 8: Compressor Initial Costs
Medium Pressure Electrical Driven Compressors
30HP – 370 $13,400.00 (electric)
40HO – 390 $15,900.00 (electric)
50HP – 5120 $$18,500.00(electric)
80HP – 24120 $27,000.00 (electric)
Questions/Comments?